Unloading, such as a long-term bet rest, immobilization, and weightlessness, causes rapid and marked muscle atrophy. Muscle atrophy caused by immobilization or unloading is associated with oxidative stress and the generation of reactive oxygen species (ROS). This book examine antioxidative effects of polyphenols, such as tea catechins and quercetin, on atrogene expression up-regulated by three dimensional (3D)-clinorotation oxidative stress unloading, such as spaceflight. Catechins and quercetin decreased the expression of atrogenes induced by oxidative stress. Supplementation of antioxidative nutrients, such as catechins and quercetin, might be beneficial for preventing muscle atrophy caused by oxidative stress